Fluid seals assemblies of various types are used in numerous applications including and not limited to sealing vehicular engine crankshafts, transmission shafts, bearing lubrication systems, compressor shaft support assemblies, and the like. The fluid seal assembly is designed to retain and seal oil or grease in a predetermined location for lubricating the shaft and to prevent ingress of environmental contaminants.
It is important to properly cure the rubber material before the seal is formed. Art is replete with various rubber curing techniques chosen on the basis of the special characteristics required to obtain and of the composition of the product having to be cured. As known to those skilled in curing art, the curing or vulcanization process consists in heating, at a suitable temperature, a rubber based material so as to form, in its structure, particular molecular bonds apt to confer the required physical/mechanical properties on the finished product. Also as known to those skilled in the curing art, the curing of extruded sections is normally carried out by adopting methods which respond to specific requirements, such as the process must be continuous, following a substantially rectilinear long path, onto which the extruded section settles down as it comes out from the extruder die, the curing of the extruded section should be efficiently obtained both on the surface and in depth.
According to a technique adopted in the past, the extruded section is caused to slide along a set of parallel idle rollers while being heated with hot air. This method however involves various negative aspects and has rapidly fallen out of use. In fact the extruded section, positioned onto the roller carpet still at the plastic state, tends to deform under its own weight even before the start of the curing process apt to confer thereon a proper mechanical strength. Furthermore, in the case of hollow sections (such as tubes), the hot air performs its action perfectly onto the outer surface of the section, but has difficulties in penetrating into the cavity.
In the motor and building industries, it is common practice to extrude sealing sections either from a black thermosetting polymeric material which incorporates one or more fillers to reduce the cost of the extrusion or from a more expensive thermoplastics material. However, in each case, there is often a requirement for the extrusion to have its characteristics changed. For example, in order to stiffen up the polymeric material of a U-sectioned edge trim or door seal, a metallic carrier is incorporated within the extrusion. Hence, there is a requirement for rubber technologists to produce special rubbers which are compatible with and therefore competitive with the harder more expensive thermoplastics materials.
Other prior art disclose a method for caring extruded sections formed of a curable rubber based material, wherein the extruded section is moved forward onto a fluid bed of melted salts, over which it floats. The portion of the extruded section emerging above the melted salts is at least partially enclosed into a compartment, and is heated at a temperature between 20° C. and 800° C. without introducing any liquid substance into said compartment.
Another curing method is disclosed in Great Britain reference No. GB-A-2109042. Here, a rubber extrusion is disclosed wherein a coating of low friction polymer such as PTFE is applied to the surface of the extruded section by means of adhesive or spraying to reduce the frictional resistance of the extrusion. With many surface coatings, which are normally very thin, it is difficult and sometimes impossible to maintain a quality check on the extrusion and it is almost impossible to measure with instruments whether the coating is present or not.
Alluding to the above, U.S. Pat. No. 4,676,856 discloses an extruded door seal which incorporates a thermoplastics polymeric carrier in place of the traditional metal carrier, around which a thermosetting polymer (rubber) is extruded. After extrusion the product is heated to cure the rubber and is then cooled so that the carrier becomes brittle so that it can be fractured along predetermined fracture lines to impart flexibility into the product, whereupon the product is heated in such a way that the carrier becomes soft again so that it can be formed into its required U-shape. Although the door seal disclosed in this specification is primarily formed of rubber, it is expensive to manufacture due to the several stages in the manufacturing process.
In addition to complex and expensive curing methods of the extrusion, there is another problem of a “seal packing” that currently exists in seal manufacturing factories, which this present invention is trying to eliminate. As it was done in the past, it would take several seals of a smaller diameter, when each of the smaller seals would be cut and then reassembled to make, for example, a larger seal with a diameter of ten meters. This process is called “seal packing”. Such seal will have at least six or even ten joints, which would result in a possible leak path at any of the joints and replacement of the seal.
The opportunity exist for an improved extruded profile that will be flexible enough in order to allow to form seals of any diameters but with only one joint thereby elimination need for the “seal packing”. There is therefore an ongoing requirement for providing a more satisfactory, less expensive product. The inventive concept as set forth further below improves the aforementioned prior art systems and methods.